Facile fabrication of hierarchical porous ZnO/Fe3O4 composites with enhanced magnetic, photocatalytic and antibacterial properties

doi:10.1016/j.matlet.2018.06.027

Materials Letters

Volume 228, 1 October 2018, Pages 207-211

https://doi.org/10.1016/j.matlet.2018.06.027 Get rights and content

Highlights

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Facile surfactant-free fabrication of hierarchical porous ZnO/Fe₃O₄ composites.
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Structural, optical and morphological characterization of prepared ZnO samples.
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ZnO/Fe₃O₄ showed better photoactivity for phenol degradation under visible light.
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ZnO/Fe₃O₄ can be easily recovered by a magnetic field along with good reusability.
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Excellent antibacterial activity against Escherichia coli over ZnO/Fe₃O₄.

Abstract

Hierarchical porous ZnO/Fe₃O₄ composites were fabricated through a facile surfactant-free method. The as-prepared samples were characterized using different instrumental techniques. The X-ray diffraction and energy dispersive X-ray results showed that the as-prepared samples were two-phase photocatalysts consisted of ZnO and Fe₃O₄. The UV–vis diffuse reflectance spectroscopy result indicated that the addition of Fe₃O₄ modified the optical properties of the photocatalysts. Under visible light irradiation, the ZnO/Fe₃O₄ exhibited enhanced photocatalytic performance for phenol degradation and Escherichia coli inactivation compared to ZnO. The photocatalytic enhancement of ZnO/Fe₃O₄ was attributed to the effective electron-hole pairs separation as verified by the photoluminescence spectra. The ZnO/Fe₃O₄ also exhibited magnetic properties, which can easily be recovered using an external magnet along with good reusability.

Introduction

Photocatalytic degradation of harmful organic pollutants and microbes disinfection using semiconductor catalysts has garnered extensive attention in recent years. Among numerous oxide semiconductors, ZnO has been well-known as a significant photocatalytic material due to its high photosensitivity, good stability, strong oxidizing power, non-toxicity and low cost [1], [2]. ZnO was also a very promising material for spintronic applications as it exhibited ferromagnetic properties [3]. It has been proven that the photocatalytic processes were surface-based reactions, and thus the photocatalytic performance of ZnO was closely related to its morphology and microstructure. Particularly, hierarchical porous ZnO architectures have received enormous interest as a class of attractive materials. Their peculiar morphology benefited the increase of specific surface area and accelerated the separation of photogenerated charge carriers [4]. However, ZnO with a relatively wide band gap can only be activated under UV light irradiation and the difficulty of catalyst separation, which limited its practical applications [2], [5]. A promising way to solve this problem was the incorporation of magnetic semiconductors to form composite photocatalysts with ZnO. Fe₃O₄ has attracted broad attention owing to its remarkable magnetic properties, strong visible light absorption, biocompatibility and low toxicity. Therefore, the incorporating ZnO and Fe₃O₄ into integrated hierarchical architectures can extend the absorption wavelength to the visible light region and enable efficient separation of catalysts using an external magnetic field.

Motivated by the above concerns, we report a simple surfactant-free approach to prepare hierarchical porous ZnO/Fe₃O₄ composites. The morphological, structural, and optical properties of the as-prepared samples were characterized using different techniques. The photocatalytic activity of the as-prepared samples was evaluated by the phenol degradation under visible light irradiation. The cycling experiments on the phenol degradation were also performed to investigate the stability of the composite photocatalysts. Moreover, the antibacterial activity of the prepared samples was tested against the E. coli. To our knowledge, there are still no reports on the phenol degradation and E. coli inactivation subjected to photocatalytic treatment over hierarchical porous ZnO/Fe₃O₄ composites.

Section snippets

Experimental

All chemicals were analytical grade and used as received. Details about the hierarchical porous ZnO microspheres and ZnO/Fe₃O₄ composites preparation, catalyst characterization, photocatalytic measurements and antibacterial activity test can be found in Supplementary material.

Results and discussion

Fig. 1a shows the XRD patterns of as-prepared samples. The diffraction peaks of 31.8° (1 0 0), 34.5° (0 0 2), 36.3° (1 0 1), 47.8° (1 0 2), 56.7° (1 1 0), 63.0° (1 0 3), 66.7° (2 0 0), 68.1° (1 1 2) and 69.2° (2 0 1) can be indexed to wurtzite ZnO (JCPDS Card No. 36-1451). Moreover, the diffraction peaks of Fe₃O₄ cubic phase can be witnessed at 30.6° (2 2 0), 43.2° (4 0 0), 54.5° (4 2 2) and 62.2° (4 4 0) (JCPDS Card No. 19-0629). The XRD patterns showed that the as-prepared composite

Conclusions

Hierarchical porous ZnO/Fe₃O₄ composites were fabricated via a facile surfactant-free chemical solution method and analyzed in details which indicated well crystallinity, good optical properties, unique morphologies and high purity. The examination of visible light photocatalytic activity showed that the ZnO/Fe₃O₄ had superior photoactivity in phenol degradation and E. coli inactivation compared to ZnO. The enhanced performance of ZnO/Fe₃O₄ was attributed to the high electron-hole pairs

Acknowledgments

This work was supported by Universiti Tunku Abdul Rahman (UTARRF/2017-C1/L02) and Ministry of Higher Education of Malaysia (FRGS/1/2015/TK02/UTAR/02/2 and FRGS/1/2016/TK02/UTAR/02/1).

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Facile fabrication of hierarchical porous ZnO/Fe3O4 composites with enhanced magnetic, photocatalytic and antibacterial properties

Highlights

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgments

Mater. Lett.

J. Clean. Prod.

J. Alloys Compd.

Mater. Res. Bull.

Facile fabrication of hierarchical porous ZnO/Fe₃O₄ composites with enhanced magnetic, photocatalytic and antibacterial properties